1. Field of the Invention
The present invention relates to vehicle structures for automobiles and particularly relates to a vehicle structure for an automobile in which crash boxes are provided at distal ends of vehicle frames extending in the longitudinal direction of the automobile.
2. Description of Related Art
A vehicle structure for an automobile has been known conventionally in which crash boxes having a rigidity lower than that of vehicle frames (front side frames or rear side frames) in the axial direction thereof (the longitudinal direction of the vehicle) are provided at the distal ends of the vehicle frames to cause buckling and deformation of the crash boxes for appropriately absorbing the impact energy at the initial stage of collision of the automobile.
For example, WO2005/010398 discloses a crash box of which original shape is in a substantially flat octagonal shape in section as an impact absorbing member. In the crash box, an inwardly recessed trench is formed in a long side thereof to increase ridges of the crash box for causing stable buckling in the axial direction thereof with no increase in weight involved, thereby ensuring a predetermined amount of impact absorption.
Formation of the trench in the crash box in a flat polygonal shape in section results in that the direction that the trench is deformed and the direction that the other part is deformed upon receipt of an impact load are reverse to each other to be cancelled, so that the crush boxes can be buckled and deformed appropriately in the axial direction thereof.